|
|
John -
I probably missed a message or two in this thread. But where did this quote come from? Max CHT is really not defineable in any useful or practical sense at all. My CHT's are alarmed at 400 and from everything I have read your do irreparable damage to the cylinder at around 425 degrees in an air-cooled aircraft engine. "Max CHT" may equate to "Max Power" in some theroetical sense, but the concept is useless as an engine management tool.
Regards,
John Schroeder
LNCE
On Tue, 10 Feb 2009 00:50:05 -0500, John Hafen <j.hafen@comcast.net> wrote:
Here¹s the quote:
³So as the mixture is leaned, power peaks first, with CHT peaking at very
close to the same point. In practical terms, if we lean to max CHT, we'll
have max power for that MP/RPM setting. Doesn't that make sense,
intuitively? Max power, max CHT? It's not precisely true, but it's close
enough.²
John
On 2/8/09 11:23 AM, "Colyn Case at earthlink" <colyncase@earthlink.net>
wrote:
John,
Did they really print that about CHT?
I don't remember that max CHT equates to anything useful although it may
correlate very well to max internal cylinder pressure (ICP), which is a bad
thing. ...but it's also affected by cylinder cooling, while EGT is (mostly)
not. Max EGT would be stoichiometric which is most efficient if your engine
can take it. Usually slightly rich of that (e.g. 50 dF ROP) is better power
but also involves more pressure before top dead center and is close to max
ICP.
There's a really scary picture you get early in the APS course which shows
how the internal cylinder pressure varies in relation to crank position when
you are running at "best power". A measurable amount of the combustion
expansion is actually pushing backwards on the crank until it comes over the
top. Great for torsional stress.
Colyn
|
|